The Arf6 GEF GEP100/13RAG2 regulates cell adhesion by controlling endocytosis of β1 Integrins
The Arf6 GEF GEP100/13RAG2 regulates cell adhesion by controlling endocytosis of β1 Integrins
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DOI：
10.1016/j.cub.2005.12.032
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发表时间：
2006-02-07
期刊：
影响因子：
9.2
通讯作者：
Casanova, JE
中科院分区：
文献类型：
--
作者：
Dunphy, JL;Moravec, R;Casanova, JE
已显示小GT受体Arf 6可调节包括β 1整联蛋白在内的一部分膜蛋白的内吞后运输，并且Arf 6功能的抑制会损害细胞粘附和运动性[1]。Arf GTP酶的活性受鸟嘌呤核苷酸交换因子（GEF）大家族的调节[2]。Arf-GEP 100/BRAG 2是一种GEF，据报道在体外对Arf 6具有特异性[3]，但在其他方面表征不佳。在这里，我们报告BRAG 2存在于两种普遍表达的亚型中，我们称之为BRAG 2a和BRAG 2b，两者都可以在体内激活Arf 6。通过siRNA消耗内源性BRAG 2导致细胞外周中的显著效应;一种这样的效应是β 1整联蛋白在细胞表面上的积累以及细胞在纤连蛋白包被的基底上的附着和铺展的相应增强。相反，Arf 6的消耗导致β 1整联蛋白的细胞内积累以及粘附和扩散降低。这些发现表明Arf 6调节β 1整联蛋白的内吞和再循环，并且BRAG 2在整联蛋白内化期间选择性地起作用以激活Arf 6。
The small GTPase Arf6 has been shown to regulate the post-endocytic trafficking of a subset of membrane proteins, including beta 1 integrins, and inhibition of Arf6 function impairs both cell adhesion and motility [1]. The activity of Arf GTPases is regulated by a large family of guanine nucleotide exchange factors (GEFs) [2]. Arf-GEP100/BRAG2 is a GEF with reported specificity for Arf6 in vitro [3], but it is otherwise poorly characterized. Here we report that BRAG2 exists in two ubiquitously expressed isoforms, which we call BRAG2a and BRAG2b, both of which can activate Arf6 in vivo. Depletion of endogenous BRAG2 by siRNA leads to dramatic effects in the cell periphery; one such effect is an accumulation of beta 1 integrin on the cell surface and a corresponding enhancement of cell attachment and spreading on fibronectin-coated substrates. In contrast, depletion of Arf6 leads to intracellular accumulation of beta 1 integrin and reduced adhesion and spreading. These findings suggest that Arf6 regulates both endocytosis and recycling of beta 1 integrins and that BRAG2 functions selectively to activate Arf6 during integrin internalization.